Temporal changes in biotypes of Haemophilus influenzae isolated from patients with cystic fibrosis.

Isolates of Haemophilus influenzae obtained sequentially over a period of 2 years from 62 patients with cystic fibrosis were biotyped. Rapid changes were seen from month to month in biotypes isolated from the respiratory tract and only a few of the patients harboured the same biotype for several months. Up to four biotypes were present simultaneously, whereas even two different biotypes were found in only one of a series of 148 patients with respiratory infections but not cystic fibrosis. Colony morphology was no guide to biotype, since the same biotype may show different colony appearances on the same plate and different biotypes may show identical colony forms.